Regulating plug for gas operated firearm



March 5, 1957 s. G. GREEN REGULATING PLUG FOR GAS OPERATED FIREARM Filed March 2, 1951 @www Mm-Get;

United Seta Peet@ REGULATING PLUG FOR GAS OPERATED FmEARM Samuel G. Green, Gray, Ga. Application March 2, 1951, Serial No. '213,640

2 Claims. `(Cl. SSV-H193.)

(Granted under Title 35, U. S. Code (1952), sec. 266) yThe invention described in thefspecific'ation and claims maybe manufactured vand used b'y or for 'the Government for governmental purposes 'without the payment of any royalty/thereon.

This invention relates to gas-operated firearms and more-particularly to improvements in mechanisms `'for gasoperation of automatic `and semi-automatic iirearins.

An object of the present invention is an improved Vgas cylinder, piston and operating rod'assembly with an improved means for mounting the gas cylinder onto the barrel.

Another object of this `invention is a gas cylinder and piston arrangement to obtain the greatest advantage of the expanded gases so that the operating rod is driven over a longer portion of the stroke.

Another object of this invention is a flexible joint between the operating rod `and the gas piston to overcome the binding of the presently used piston and operating rbd, and to facilitate assembly anddisassembly o'f theweapon.

Another object of this invention is Ia volumeand pressure control so 'as to provide a reserve for operation of the rifle under adverse conditions, such as cold, rain, wear, etc., and to provide avolurne control which can be regulated independently of the pressure control.

Another object of this invention is la simplified form of sight mounting in combination with a more efficient 'and simpler :gas cylinder mounting.

Another object of this invention is to provide an automatic weapon with straight operating rod.

Another object of this invention is a gasmechanism assembly that can accommodate a longer gas piston which aids materially in sealing of the gas between 'the piston and the gas cylinder wall, lan'dwhich thereby permits more yliberal tolerances in the manufacture of these parts.

`Another object of this invention is to `provide afsemi- `spherical recess in the `head vof the piston to aid .in break- Aing up 'of residue deposits onthe 'gas piston and operating parts.

Another object of this invention is a replaceable gas piston :so 'as to maintain a desired clearance between the gas piston and 'the 'gas cylinder, and `to maintain such :clearance even in cases of Worn gas cylinders, by using Y 'fever-sized pistons, Vif necessary.

Another object ofthis invention is to provide a simple Vfield replacement lfor the gas piston so as to yavoid expensive .replacements of the operating rod assembly where only 'the gas piston is defective.

A Ifurther object oithis invention is ana'cljusta'ble means for l'obtaining maximum power of operation under adverse conditions, 'such as rain, mud, extreme cold, etc., fand at the same time fo provide means for ladjusting a particular rie to obtain the best possible performance as to reserve and dependability without using excess power wh'enit is not needed.

The speciiic nature "of this invention ,as well as other Aobjects and advantages thereof will clearly appear from Nce .f2 `the following description and accompanying drawings in which:

Fig. l is a longitudinal, sectional view of the muzzle end of a riile employing the improved mechanisms of this invention for gas-operated automatic and semiautomaticiirearms.

Fig. 2 is an enlarged Yfragmentary view of the gas cylinder and bleeder.

Fig. 3 is a sectional `view `taken along lines 3-3 of Figt'l.

Fig. 4 is la l.sectional `view taken along lines 4-4 of Fig. l.

Fig. 5 is a longitudinal sectional view showing amodication of the coupling between the piston and the operating rod.

Fig. 6 is a longitudinal, sectional view showing another modification of .the coupling between the piston and the operating rod.

Fig. 74is a chart whereon are plotted curves comparing the results obtained with :the gas-operated firing mechanism employed inthe currently used U. S. Ml rifle and those obtained with the same type rifle incorporating the improvements of the present invention.

In the conventional mechanism for vgas operation of automatic and semia'utomatic firearms, as exemplied by the standard type M l ride, the gas port is placed approximately li inches .from the muzzle. Furthermore because ot assembly requirements, the piston Vhas a bearing length of less than 56 .of an inch, and a diameter of ,526 inch; These dimensions .are :contrary to Vthe minimum requirement according to which the piston bearing length should Lbe at least one piston diameter. However the shorter piston hearing length and the oli-setting of the tube of the operating rodrare necessary to facilitate assembly ofjrhe'curr'ent type of weapon.

p Witlrthe gasport located near the muzzle in the standard rifle, proper operation thereo requires `almuzzle pressure of approximately V680() pounds. And lsince ,the `gas port .size and the diameter .of the piston have very little eect on the ,amount of power taken oi, as the time o'f travel of-thebllet from the port to the muzzle is too `sh'or'tto maintain the pressure over a .work period necessary to gain the reqt'lired energy for reliable operation,

`this arrangement requires `the maintenance of a critical dimensional relation'between the piston diameter and the `cylinder diameter. 'Moreover the expansion space is a 'piston within required close tolerances is high.

Furthermore these critical conditions are aggravated by theparticular mounting ofthe gas V cylinder of the standard vriie which results 'in leakage of gas between the gas `cylinder and the barrel. And since the front sight ismounted on the gascylinden any looseness between the v.gas cylinder and 'the barrel `tli'rectly affects the accuracy of 4the-sight.

Ihese disadvantages are overcome by the improvements in accordance withthe present invention, which provides .an improved and novel lgas-operadag mechanism and method for mounting the saine, which permits the use of a ystraight operating rod.

More specifically, rcerence numeral -1 designates the barrel. Similar reference characters are used to designate similar .parts in the various gures of the drawing. The

gas cylinder bracket 2 is mounted onto barrel 1 by an Allen type set screw 3. The gas port 4 in barrel 1, which is located at approximately 4 to 6 inches from the muzzle communicates with a corresponding gas vportj5 in cylinder bracket 2. Spline slot 6 in barrel 1 and spline slot 7 in cylinder bracket 2 receive spline key 8. In the `assembly of the mechanism spline key 8 is put into position in spline slot 6 of barrel 1. Cylinder bracket 2 is then slipped over barrel 1 until the tip of Allen type set screw 3 is in alignment with recess 9 in key 8 whereupon Allen type set screw 3 is fastened into the threaded portion of base 10 in cylinder bracket 2 until the tip bears snugly against key 8. This brings gas port 5 in cylinder 2 automatically into alignment with said gas port 4 in said barrel 1, and anchors bracket 2 to barrel 1; it also anchors key 8 in spline slot 6 against rotational, longitudinal, and llateral movement and forms a seal between the underside of barrel 1 and the surface of cylinder bracket 2 in contact therewith. Shoulder 11 is provided on barrel 1 to take the rearward thrust of cylinder bracket 2 while the forward end 12 of key slot 6 provides an abutment to prevent the gas cylinder bracket 2 and key 8 from moving in a forwardly direction.

The foregoing arrangement of applicants improved mounting also eliminates the need for removal of the gas cylinder bracket for full stripping and cleaning.

As clearly seen in Figs. 1 and 3, gas cylinder bracket 2 is a double looped unitary piece with its upper loop arranged to Ireceive barrel 1, as previously described, and its lower loop forming the forward end of a gas cylinder 2' lying immediately below and parallel with barrel 1, and extending rearwardly toward the receiver parts of the weapon (not shown). Other means (not shown) and rearwardly disposed on barrel 1, also serves to support the gas cylinder bracket 2 in juxtaposition with the barrel in the well known manner.

A gas receiver or expansion chamber, discussed hereinafter, is that portion of gas cylinder 2' defined by the rearward face of pressure regulator 28 and the forward face of piston 13, the piston beingy in the forwardmost position.

Gas piston 13 is reciprocable in gas cylinder 2 and has a semi-spherical recess 14 in its head to aid in the breaking up of residue deposits on gas piston 13 `and other operating parts. Gas piston 13 has an overall length of about one and one half times its diameter, and the resulting arrangement permits full advantage to be taken of annular grooves 15 for checking the by-pass or escape of operating gases. Piston rings (not shown) may also be used for similar purposes with piston 13. These features as well as an increased piston diameter permit greater manufacturing tolerances of the various parts, as an ideal ratio of diameter to piston length can be more readily achieved.

By slightly increasing the distance between the center line of the barrel, and the center line of gas cylinder 2' and by providing an articulated joint between gas piston 13 and operating rod 16 the operating rod tube accordirig to applican-ts invention is made straight instead of o set.

With the conventional rigid joint between the piston and the operating rod, the misalignment of the track on the receiver (not shown) and the gas cylinder which is mounted onto the barrel results in binding of the gasoperated mechanism, particularly when the weapon is heated. For this reason, the conventional assemblyvof the rie, which consists of a short piston fastened securely to the operating rod, not only necessitates a short piston bearing length but also involves a very inefiicient relation between the piston and cylinder.

In order to overcome these disadvantages and to permit utilization of Ithe improved and more efficient gas-operated mechanism, `applicant provides a flexible joint 17 between the gas piston 13 and a hollow operatingrod 16. Coupling link 18 has a diameter which is slightly smaller than the bore of operating rod 16 and is provided with a diametrical hole 19 to receive a pin 20 for purposes of fastening coupling link 18 to operating rod 16 by means of a corresponding hole 21 in operating rod 16. The at end 22 of coupling link 18 engages operating rod spring 23 while bushing or shoulder 24 of coupling link 18 rests against the end of operating rod 16. Flexible coupling between coupling link 18 and piston 13 is provided by means of pin 24 which permits relative rotational movement between these two parts in a plane of the drawing. The end of the piston 13 nearer coupling link 18 has a biurcated extension wi-th two prongs or tines 25, the contours of which are indicated by the dotted line 26 in Fig. 1 of the drawing. The space formedAbetween'two prongs 25 receives the centrally protruding tongue 27 which forms an integral part with coupling link 18. Pin 24' extends through a bore in prongs 25 and in tongue 27 whereby relative rotational movement in the plane ofthe drawing may take place between coupling link 18 and `piston 13. Other Imodifications of llexible couplings are illustrated in Figures 5 and 6 and will be more ful-ly described below. It should also be noted that piston 13 is purposely made to overlap with its contact surface in gas cylinder Z', so as to provide a wiping action to clean piston 13.

The forward end of the gas cylinder 2 is 'closed by a gas cylinder screw 28 having a counterbore 28' at the inner end thereof. The outer periphery of the walls of counterbore 28 are provided with a threaded portion 29 that is adapted for mating engagement with a recessed internal threaded portion 30 on the inner periphery of the wall of the gas cylinder 2. A piston receiving portion 30 is located in the gas cylinder 2' adjacent to and rearwardly of the recessed threaded portion 30 for guiding the piston 13 during its reciprocakmovement. As shown in Fig. 2 of the drawing when the cylinder screw 28 is screwed into the forward end of the gas cylinder 2', the counterbore 28' is coaxial with the piston receiving portion 30. As shown in the drawing the diameter ,of the counterbore 28' is slightly greater than the diameter of the piston receiving portion 30'.

The cylinder screw 28 is centrally bored through its base with a valve 31 positioned in this bore. The yvalve 31 is normally urged toward the right, as shown in the drawing, by a spring 32 so that a bevelled head 33 seals the gas cylinder 2. The extension Yarm of a grenade discharger (not shown) causes valve 31 to open when placed in position on the barrel 1, as is current practice with the standard M1 rifle. The cylinder screw 28 has three sizes of ports, a large one 34, a medium sized one 35, and a small one 36. As illustrated in Fig. 3 the medium sized port 35 is shown in alignment with gas ports 4 and 5 in barrel 1 and cylinder bracket 2 respectively. In order to provide a minimum volume in the expansion chamber of gas cylinder 2 the smallest port 36 is brought into alignment with, gas ports 4 and 5. With successively largerl gas ports 35 and 34 increasingly larger expansion chamber volumes will be provided as the cylinder screw 28 must be rotated in a counterclockwise direction as viewed in Fig. 4 in order to bring the larger ports 35 and 34 into alignment withV ports 4 and 5, thereby gradually withdrawing the cylinder screw 28 to increase the volume in the expansion chamber. A locking mechanism is provided with cylinderrscrew 28 which retains the cylinder screw in position so that any selected one of ports 34, 35 or 36 is retained in alignment with gas ports v4 and 5. Locking recesses 37 in cylinder bracketZ receive spring-loaded locking detent 38 which is secured to cylinder screw 28 by means of fastening screw 39. Springv 40 normally urges detent 38 to the left (as shown in the drawing) so that it will be firmly seated in a selected locking recess 37. If it is desired to change to a different size of gas port, locking detent .38 is pulled forwardly against v the bias, Of'spring 40 pressure from its recess 37, whereupon cylinder screw 28 together with detent 38 may Ebe v rotated until the detent 3S is in alignment With the selected recess 37. Detent 3'8 is then released and spring 40 will again seats detent3`8 firmly in 'the selected recess 37, 'which bring the selected gas port in cylinder screw '28 automatically into alignment with gas ports 4 and 5, and further automatically adjusts the volume of the expansion chamber.

Cylinder screw 28 is also provided with a pressure regulator which consists of a screw plug v41. centrally apertured as at 42. The centrally located vent 42 provides for minimum discharge of .gases from the expansion chamber through a communicating channel 45, and is at all times effective. Two further vents 43 .and '44"are Provided in screw plug 41for regulating, the amount of additional discharge. 'These two further vents 43 and 44 come into pl'ay when screw plug 41 is unscrewed and thereby unseated from its end position, .the amount of additional discharge through vents 43 and 44 depending on the particular setting of screw plug 41. Cleaning port 46 which is in alignment with ports 4 and 5 `is sealed by cylinder screw 28, but permits ready access 'to gas ports 4 S for purposes of cleaning the same upon removal of the gas regulator. it is thus seen that thevolumfe control may be regulated in the novel regulator 2S independently of the pressure contr-o1 so that excess `pressure at, a given volume can be discharged. This .featureserves as a selfcleanenas Aheavy particles from the vvdischarged gas will be permitted to escape the gas cylinder 2'.

Figures 5 and 6 illustrate modifications 'of the flexible joint illustra-ted in Fig. l; bot-hof the modifications `illustrate universal joints instead of the flexible joint 17 of Fig. l.

More specifically operating rod 16 of Fig. 5 is connected to coupling link 18' by means of pin 20 which is inserted into bores 21 and 19 in operating rod 16 and coupling link 18', while the at end 22 of coupling link 18 rests against operating spring 23 and shoulder 24 rests against operating rod 16 much in the same manner as pointed out with respect to Fig. 1. Tongue 27 of Fig. l is replaced in Fig. 5 with a cylindrical shaft 47- having a threaded portion 48 on the outside thereof and a semispherical recess 49 at its end in which ball 50 of the universal joint rests. Ball 50, shank 51 and cylinder 52 form one integral member. The threaded portion of cap 53 engages the threaded portion 48 of cylindrical shaft 47. The curvature of the end portion S4 of cap 53 is made approximately equal to the curvature of ball 50. Opening 55 in end portion S4 is made large enough so that shank 51 and cylinder 52 will freely pass therethrough while preventing passage of ball 50. The universal joint illus-trated in Fig. 5 is assembled by slipping shaft 52 and shank 51 through opening S5 until ball 50 rests in curved end-portion 54; cap 53 is then screwed onto cylindrical shaft 47 whereby a universal joint is provided between elements 16, 18', 47 and 54 on the one hand and elements 50, 51 and 52 on the other. Piston 13 which has a threaded bore is screwed onto vthe threaded portion of cylindrical shaft 52. Locking screw 56 is then inserted into the threaded bore of piston 13 to retain shaft 52 in its position. It is thus seen -that a universal joint is provided between operating rod 16 and piston 13' which is highly desirable for gun mechanisms to provide against misalignment in all planes.

Figure 6 illustrates a further modification of the universal joint shown in Figure 5. Operating rod 16 is secured to coupling link 18 by means of pin 20 which is inserted into bores 21 and 19 in operating rod 16 and coupling link 18, while the flat end 22 of coupling link 18" rests against operating spring 23 and shoulder 24 rests against operating rod 16 as pointed out with respect to Fig. l. Coupling link 18" has a threaded bore which receives threaded cylinder 52' which forms an integral part with shank 51 and ball 50. Threaded cylinder 52' has also a diametrical hole 57 which receives pin 20. Piston 13" has a bore 58 which is large enough to permitfree passage therethrough of cylinder 52' and shank 51' but which prevents passage of ball 50'. The other end of (piston '13" has a threaded bore S9 which is large enough to permit free passage of ball 50. The transition from threaded 'bore '59 to smaller bore 5S in piston 13" is shaped in such a manner as to conform to the curvature of ball 50' which rests therein in its assembled position. Locking screw '60 which has a semi-spherical recess `61 adapted to receive ball 50' in rotatable engagement, serves also to hold ball S" in its assembled position.

-Figure 7 compares the results obtained when astanda'rd Ml .rifle is modified by replacing the conventional g'as system with a system having an adjustable gas chamber. Curve 62 represents the modified rifle with the sleeve 29 set :to provide a gas chamber having a volume equal to the standard `MA1 rifle but with the gas port placed a'pproximately 4 inches rearwardly of the muzzle. With this adjustment the opposed contiguous faces of piston 13 and valve 33 are spaced a small distance apart. In Figure 7 #the sliding movement of the piston'was plotted as abcissae, while corresponding load impacts were plotted as ordinates. The initial energy required for proper operation of the ,gun mechanism, which is equal to .030 on the load impact scale, persisted for a short period of time, with a travel of approximately a of an inch for the operating rod and piston, after which the effective energy dropped off rapidly. In this respect the curve simulated conditions existing for the standard Ml rifle, without gas chamber adjustment, although the modedrifle gave slightly better results.

Curve 63 represents the modified riiie utilizing Athe same ammunition but with the adjustable gas chamber volume increased to give a spacing of approximately 1% of an inch between piston head and valve face and with the gas port still at 4 inches from the muzzle. This condition is illustrated in Figures 1 and 2. This curve 63 shows clearly that a somewhat greater average load-impact is obtained at early movements of the operating rod and maintained for approximately 2% inches stroke, with a following gradual drop off which increases as the full stroke is approached but which does not drop below .030 until the travel is approximately 3/2 inches. Since both curves indicate only average load-impacts, actual minima which occur during the stroke fall below these average curves 62 and 63. However since a greater average load impact is obtained with the improved gas operating mechanism in accordance with the present invention, such minima do not fall below the necessary load impact of .030 over a distance of 2% inches, which represents the energy level necessary for proper operation of the mechanism.

From the foregoing description it is quite clear that the improved gas operating mechanism in accordance with the present invention results in more uniform power application over a longer period, and will eliminate the necessity of maintaining a relatively high muzzle pressure, which is advantageous in controlling flash and smoke. It also provides a novel pressure adjustment which is important as marginal performance under adverse conditions may be readily corrected thereby.

Furthermore the present invention permits a more favorable working ratio between the available powder pressure and the operating rod by placing the gas port at a distance of between 1S and 25 percent of the bullet travel in the rifle from the muzzle of the rifle, by increasing the piston diameter to obtain a 25 percent greater working area, and by increasing the piston length to 11/2 times its diameter.

Other modification of the construction of 'the gas-operated mechanism may readily occur to anyone skilled in the art, and while I have shown and described several embodiments of my invention, it will be understood that those embodiments are merely for the purpose of illustration and description, and that various other forms and modifications may be devised within the scope of my invention, as defined in the appended claims.

- amanece l v1 claim;

having a counterbore formed in its inner end, said counterbore having an internal diameter as large as the internal diameter of said piston receiving portion, the external periphery of the wall of said counterbore having screw threads adapted for mating engagement with said threaded portion so that said counterbore will be substantially aligned with said piston receiving portion, a piston longitudinally reciprocable in said cylinder, the forward face of said piston forming with said counterbore a gas receving chamber, a plurality of radially disposed ports of varying sizes formed in the wall of said counterbore, radially aligned ports in the wall of said barrel and in said cylinder, said screw being longitudinally adjustable to vary the capacity of said gas receiving chamber, and to selectively align one of said radially disposed ports with said radially aligned ports so as to aiord a direct passage between said barrel and said gas receiving chamber, and a screw plug threadedly engaged in said cylinder Escrew, a vent in said screw plug coaxial therewith providing a constant communication between said expansion chamber and the atmosphere, other vents longitudinally disposed in said screw plug for communicating said expansion nally adjustable to vary the gas discharge through said 8 other vents so as to maintain a predetermined maxim pressureY in said expansion chamber.

2. A gas operated firearm as set forth in claim 1 wherein the diameter of said counterbore is slightly larger than the diameter of said piston receiving portion.

References Cited in the tile of this patentl Y UNITED STATES PATENTS 626,905

Hanson June 13, 1899 687,130 Dawson, et al. Nov. 19, 1901 1,195,693 Lewis Aug. 22, 1916 1,291,690 Smith Jan. 14, 1919 1,359,726 Morrison Nov. 23, 1920 t 1,441,807 Horan Jan. 9, 1923 1,446,635 Berthier Feb..17, 1923 1,738,501 Moore Dec. 3, 1929 1,907,163 White May 2, 1933 2,093,706 Browning Sept. 21, 1937 2,144,241 Eiane s Jan. 17, 1939 2,149,512 Eiane Mar. 7, 1939 2,340,293 Balleisen Feb. l, 1944 2,369,669 Garand Feb. 20, 1945 2,390,738 Rutherford et al. Dec. 11, 1945 2,416,287 Coates et a1 Feb. 25, 1947 2,462,119 Moore Feb. 22, 1949 2,494,889 Maillard Jan. 17, 1950 2,503,272 obert Apr. 11, 1950 FOREIGN PATENTS l France Mar. 7, 1951 

